When using the built-in functionality of a VINT port (Digital Input, Digital Output, VoltageRatioInput, or VoltageInput) you need to use setIsHubPortDevice(1), so it knows that it's opening the port itself, and not a VoltageRatioInput channel belonging to a device connected to that port. You'll still have to set HubPort, but not channel.

VoltageRatio is between 0 and 1; it just looks like you're measuring a very, very small voltage change on that channel. If you're expecting higher values, it's possible the wrong port has been opened, since that looks like the kind of data you'd get from a port that has nothing connected to it.